1. Field of the Invention
The present invention relates to a transaxle including a frictional transmission mechanism and a differential mechanism.
2. Related Art
As disclosed by JP 2004-36836 A (hereinafter, “Reference 1”), there is a well-known conventional frictional transmission unit. This frictional transmission unit includes an input shaft to be drivingly connected to a power source, a frictional drive disc fixed on the input shaft, an output shaft extended perpendicular to the input shaft, and a frictional driven disc fitted on the output shaft so as to be unrotatable relative to the output shaft and so as to be axially slidable along the output shaft. A peripheral edge of the driven disc frictionally contacts any portion of a disc surface of the drive disc. The driven disc is slid along the output shaft so as to change the contact position of the driven disc with the drive disc, i.e., the position of the driven disc relative to the drive disc, thereby changing the rotational direction and speed of the output shaft.
Reference 1 also discloses some lawn mowers each of which serves as a working vehicle equipped with a transaxle that includes the frictional transmission unit. Hereinafter, each of the lawn mowers is simply referred to as a “vehicle”. The input shaft of the frictional transmission unit serves as an input shaft of the transaxle to be drivingly connected to an engine equipped on the vehicle. The transaxle also includes a differential unit differentially connecting right and left output shafts of the transaxles that are drivingly connected to respective right and left axles of drive wheels. The output shaft of the frictional transmission is drivingly connected to an input portion of the differential unit via a reduction gear train. Therefore, power of the engine is transmitted to the right and left axles via the transaxle while the rotational direction and speed of the output shaft is changed by the slide of the driven disc along the output shaft of the frictional transmission unit so as to change the rotational direction and speed of the right and left axles.
In the embodiment disclosed by Reference 1, the frictional transmission unit and the differential unit are essentially independent of each other. To drivingly connect the frictional transmission unit to the differential unit, the reduction gear train, including a counter shaft and counter gears, must be interposed between the frictional transmission unit and the differential unit, thereby increasing parts and costs.
Further, the transaxle must be expanded because the transaxle must incorporate the frictional transmission unit, the reduction gear train and the differential unit, must ensure the arrangement of the friction drive and driven discs contacting each other in a perpendicular manner and must ensure the slidable range of the driven disc in parallel to the right and left axles.